Scruel O, Sener A, Malaisse W J
Laboratory of Experimental Medicine, Brussels Free University, Belgium.
Mol Cell Biochem. 1997 Oct;175(1-2):263-9. doi: 10.1023/a:1006834010660.
Human B-cell glucokinase displays sigmoidal kinetics towards D-glucose or D-mannose, but fails to do so towards D-fructose. Yet, D-glucose, D-mannose and 2-deoxy-D-glucose confer to the enzyme positive cooperativity towards D-fructose. For instance, in the presence of 5 mM D-[U-14C]fructose, its rate of phosphorylation is increased to 214.3 +/- 11.0%, 134.0 +/- 4.3% and 116.5 +/- 3.0% of paired control value by D-glucose, D-mannose and 2-deoxy-D-glucose (each 6 mM), respectively. D-glucose and, to a lesser extent, D-mannose also display reciprocal kinetic cooperativity. D-fructose, however, fails to affect D-glucose or D-mannose phosphorylation under conditions in which positive cooperativity is otherwise observed. These findings are relevant to the reciprocal effects of distinct hexoses upon their phosphorylation by B-cell glucokinase and, as such, to the metabolic and functional response evoked in pancreatic islet B-cells by these sugars, when tested either separately or in combination.
人B细胞葡萄糖激酶对D-葡萄糖或D-甘露糖呈现S形动力学，但对D-果糖则不然。然而，D-葡萄糖、D-甘露糖和2-脱氧-D-葡萄糖赋予该酶对D-果糖的正协同性。例如，在存在5 mM D-[U-14C]果糖的情况下，D-葡萄糖、D-甘露糖和2-脱氧-D-葡萄糖（各6 mM）分别将其磷酸化速率提高到配对对照值的214.3±11.0%、134.0±4.3%和116.5±3.0%。D-葡萄糖以及程度稍低的D-甘露糖也表现出相互动力学协同性。然而，在其他情况下观察到正协同性的条件下，D-果糖未能影响D-葡萄糖或D-甘露糖的磷酸化。这些发现与不同己糖对其被B细胞葡萄糖激酶磷酸化的相互作用有关，因此也与这些糖单独或组合测试时在胰岛B细胞中引发的代谢和功能反应有关。
